U.S. patent number 4,331,697 [Application Number 06/183,377] was granted by the patent office on 1982-05-25 for novel heparin derivative, method for production thereof, and method for rendering biomedical materials antithrombotic by use of the novel heparin derivative.
This patent grant is currently assigned to Teijin Limited. Invention is credited to Hiroo Inata, Akira Kudo, Makoto Ogasawara.
United States Patent |
4,331,697 |
Kudo , et al. |
May 25, 1982 |
Novel heparin derivative, method for production thereof, and method
for rendering biomedical materials antithrombotic by use of the
novel heparin derivative
Abstract
A heparin derivative in which at least 0.5% of the entire
hydroxyl groups of heparin are in the form of an ester of the
following formula ##STR1## wherein R.sub.1, R.sub.2 and R.sub.3
each represent a hydrogen atom or an alkyl group having 1 to 6
carbon atoms; a method for producing aforesaid heparin derivative
which comprises reacting heparin with a halide or anhydride of an
unsaturated carboxylic acid of the formula ##STR2## wherein
R.sub.1, R.sub.2 and R.sub.3 are the same as defined above; and a
method for imparting antithrombotic activity to a biomedical
material, which comprises treating that surface of the biomedical
material which makes contact with the blood with actinic light in
the presence of aforesaid heparin derivative.
Inventors: |
Kudo; Akira (Hino,
JP), Inata; Hiroo (Hino, JP), Ogasawara;
Makoto (Hino, JP) |
Assignee: |
Teijin Limited (Oraka,
JP)
|
Family
ID: |
22672557 |
Appl.
No.: |
06/183,377 |
Filed: |
September 2, 1980 |
Current U.S.
Class: |
427/2.11;
427/2.12; 427/2.24; 427/2.25; 427/2.28; 427/2.3; 514/56;
536/21 |
Current CPC
Class: |
C08B
37/0075 (20130101); A61L 33/0011 (20130101) |
Current International
Class: |
A61L
33/00 (20060101); C08B 37/00 (20060101); A01N
001/02 () |
Field of
Search: |
;424/183 ;536/21
;427/2 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Silverberg; Sam
Attorney, Agent or Firm: Sherman & Shalloway
Claims
What we claim is:
1. A method for imparting antithrombotic activity to a biomedical
material, which comprises treating that surface of the biomedical
material which makes contact with the blood with actinic light in
the presence of a heparin derivative in which at least 0.5% of the
entire hydroxyl groups of heparin are in the form of an ester of
the following formula ##STR8## wherein R.sub.1, R.sub.2 and R.sub.3
each represent a hydrogen atom or an alkyl group having 1 to 6
carbon atoms.
2. The method of claim 1 wherein at least the surface of said
biomedical material is a hydrophilic substance.
3. A method for imparting antithrombotic activity to a biomedical
material, which comprises forming at least that surface of the
biomedical material which makes contact with the blood from a
polymer having a carboxylic acid halide group and/or a carboxylic
anhydride group in the side chain, and treating said surface with a
solution of heparin wherein at least 0.5% of the entire hydroxyl
groups of heparin are esterified.
4. The method of claim 1 wherein both R.sub.1 and R.sub.2 are
hydrogen atoms and R.sub.3 is a hydrogen atom or a methyl
group.
5. The method of claim 1 wherein the treatment with actinic light
is conducted at a temperature of from -10.degree. C. to 70.degree.
C.
Description
This invention relates to a novel heparin derivative, a method for
production thereof, and a method for imparting antithrombotic
activity to that surface of a biomedical material which makes
contact with the blood. More specifically, this invention pertains
to a novel heparin derivative which is bound to a biomedical
material through an active unsaturated group and imparts
antithrombotic activity to the biomedical material, a method for
producing said heparin derivative, and to a method for rendering a
biomedical material antithrombotic.
In recent years, with a great advance in medical therapy, materials
which make direct contact with the blood have been used on many
occasions, for example in temporarily conducting the blood out of
the body, or substituting artificial organs for organs within the
body which make contact with the blood. Such materials include, for
example, vascular catheters, cannulas, monitoring tubes, artificial
kidneys, artificial heart-lungs, extracorporeal circuits for
auxiliary circulating devices, A-V shunts, vascular prostheses,
artificial heart valves, temporary blood by-path tubes, and
film-like or hollow filament-like dialysis membranes.
Conventional materials (to be referred to as biomedical materials)
which make direct contact with the blood are made from glass,
metals, plastics such as soft vinyl chloride resins and silicone
resins, and rubbers such as natural rubber. It is known that upon
contact with such a biomedical material, the blood easily
coagulates and forms a thrombus on its surface. The thrombus has a
great danger of stopping the blood current or moves with the blood
current to cause complications such as pulmonary thrombosis,
cerebral thrombosis or myocardial infraction. In using these
biomedical materials, therefore, it is the conventional practice to
prevent thrombus formation by systemically administering an
antithrombotic agent such as a preparation comprising heparin,
coumarine, sodium citrate, etc. thereby to render the blood
non-clotting. Systemic administration of heparin, etc., however,
has the defect of causing a marked danger of bleeding.
If antithrombotic activity can be imparted to a biomedical
material, it would be possible to prevent thrombus formation
without systemically administering heparin, etc., and to safely
perform medical treatment and diagnosis using these biomedical
materials.
Some methods have been reported in the past about a method of
imparting antithrombotic activity to a biomedical material by
treating its surface with heparin known as an anticoagulant. One
method comprises covalently binding heparin itself to the surface
of a biomedical material to fix it there (see, for example, B. D.
Halpern, et al., Interaction of Liquids at Solid Substrate, ed. R.
F. Gould, Am. Chem. Soc., Pub. 1968; and A. S. Hoffman et al.,
TASAIO, 18, 10 1972). This method, however, was found to be
ineffective, or effective only to a small extent. As a result, it
was thought that heparin generally loses as antithrombotic activity
or its antithrombotic activity decreases when it is covalently
bound with another substance or compound.
There was suggested a method which comprises adhering or
impregnating heparin to the surface or in the surface layer of a
biomedical material, and releasing the heparin gradually into the
blood during use [see, for example, R. I. Leininger, et al.,
Science, 152, 1625, 1966; A. Rembaum, et al., J. Macromol. Sci.
Chem., A4 (3), 715, 1970; E. W. Merrill, et al. TASAIO, 12, 139,
1966]. According to this method, it is extremely difficult to
control the release of heparin in such a manner that a moderate
amount of heparin can be released over a long period of time.
Hence, the antithrombotic activity lasts only for a short period of
time, or an excessive amount of heparin is released to cause a
danger of bleeding.
It is an object of this invention to provide a compound which can
impart antithrombotic activity to a biomedical material while being
covalently bound to it.
Another object of this invention is to provide a method for
rendering the surface of a biomedical material antithrombotic over
a long period of time, which comprises treating said surface with a
compound capable of exhibiting antithrombotic activity while being
covalently bound to that surface of the biomedical material which
comes into contact with the blood.
The present inventors made extensive investigations in order to
achieve the above objects, and found that these objects of the
invention can be achieved by using an ester derivative of heparin
with a carboxylic acid having a specified unsaturated group.
Thus, according to the present invention, there is provided a
heparin derivative in which at least 0.5% of the entire hydroxyl
groups of heparin are in the form of an ester represented by the
following formula ##STR3## wherein R.sub.1, R.sub.2 and R.sub.3
each represent a hydrogen atom, or an alkyl group having 1 to 6
carbon atoms.
The heparin derivative of this invention is a novel compound. First
World Biomaterials Congress (Baden near Vienna, Austria, Apr. 8-12,
1980), Final Programme Book of Abstracts 1.3.6 describes the
reaction of heparin with acrylic acid. Since this reaction is
carried out in the presence of cerium IV, the reaction product is a
compound in which heparin is bonded to acrylic acid through a
carbon-carbon bond. Accordingly, this compound quite differs from
the heparin derivative of this invention in which heparin is bonded
to the carboxylic acid through an ester linkage.
The accompanying drawings show infrared absorption spectra of the
novel heparin derivatives of this invention.
FIG. 1 is an infrared absorption spectrum of the heparin derivative
obtained in Example 1;
FIG. 2 is an infrared absorption spectrum of the heparin derivative
obtained in Example 2; and
FIG. 3 is an infrared absorption spectrum of the heparin derivative
obtained in Example 3.
FIG. 4 is an infrared absorption spectrum of heparin used in
synthesizing the heparin derivatives.
An absorption of an ester (--COO--), which is not seen in FIG. 4,
appears at 1720 cm.sup.-1 in FIGS. 1 to 3.
Heparin usually employed as an antithrombotic agent may be used as
the starting heparin in the production of the novel heparin
derivative of this invention. Heparin is usually extracted as a
mucopolysaccharide from animal tissues, for example from hog
intestine or whale intestine. It is commercially available as
sodium heparin. It shows the activities described in Japanese
Pharmacopoeia C-1235, or U.S. Pharmacopoeia XIX, p 229 (1975).
Those which are therapeutically acceptable can be used in this
invention.
As shown by formula (I), in the heparin derivative of this
invention, an unsaturated group is introduced into the alcoholic
hydroxyl moiety of heparin through an ester linkage. The site of
introduction of the unsaturated group may be at any of the many
alcoholic hydroxyl groups, and the number of such unsaturated
groups is one or more. The ratio of introduction of ester linkages
should be such that at least 0.5% of the entire hydroxyl groups of
heparin are converted to the ester represented by formula (I).
The ratio of introduction, as used herein, is calculated as
follows:
Heparin is usually a polymeric compound containing a disaccharide
of the following structural formula ##STR4## as one unit. (Not all
of the units have three SO.sub.3 H as in the above formula. Also,
SO.sub.3 H is sometimes present in the form of SO.sub.3 Na. But
these facts are not relevant to the calculation of the ratio of
introduction of ester groups.)
As the number of carbon atoms in one unit is 12, the molecular
weight [H] of one unit of heparin is calculated as follows from the
amount of carbon [C.sub.1 ]% determined by elemental analysis.
When ester groups are introduced, the ratio of introduction [D%] of
the ester groups can be calculated from the following equation.
##EQU1## wherein [C.sub.2 ] is the amount of carbon determined by
elemental analysis of esterified heparin,
[M] is the amount of the ester represented by formula (I), and
[N] is the number of carbon atoms of the ester of formula (I).
As the ratio of introduction D% obtained corresponds to two
hydroxyl groups, the ratio of introduction for one hydroxyl group
is D/2. The D/2 value represents the ratio of introduction of ester
linkages into the entire hydroxyl groups of heparin. A specific
method of calculating this introduction ratio is shown in Example 1
to be given hereinbelow.
When an infrared absorption spectrum of the heparin derivative is
taken by an infrared spectrophotometer (JASCO-A-102, a product of
Nippon Bunko K.K.), an absorption of the ester is located at 1720
cm.sup.-1 even when the ratio of introduction of ester groups is
1%. The maximum of the ratio of introduction of ester groups is
100%, but introduction of substantially 100% ester groups causes a
great industrial loss. The ester introduction ratio may be not more
than 80%, and at times, not more than 50%. Preferably, 1 to 80%,
more preferably 3 to 50%, of the entire hydroxyl groups of heparin
are converted to the ester represented by formula (I).
In formula (I), each of R.sub.1, R.sub.2 and R.sub.3 represent a
hydrogen atom or a lower alkyl group having 1 to 6 carbon atoms.
These groups may be the same or different. Examples of the lower
alkyl group are methyl, ethyl, propyl, isopropyl, butyl, isobutyl,
heptyl and hexyl groups. Alkyl groups having 1 to 4 carbon atoms
are preferred and a methyl group is especially preferred. Most
preferably, both R.sub.1 and R.sub.2 are hydrogen atoms, and
R.sub.3 is a hydrogen atom or a methyl group.
The heparin derivative of this invention retains the inherent
antithrombotic activity of heparin. Since an unsaturated group
which is intrinsically irrelevant to the antithrombotic activity is
introduced, the heparin derivative can be fixed to the desired site
of a biomedical material by utilizing the activity of the
unsaturated group. The heparin derivative exhibits superior
antithrombotic activity even when it is in the fixed state.
The novel heparin derivative of this invention can be produced by a
method which comprises reacting heparin with a halide or anhydride
of an unsaturated carboxylic acid of the following formula ##STR5##
wherein R.sub.1, R.sub.2 and R.sub.3 are as defined hereinabove, to
esterify at least 0.5% of the entire hydroxyl groups of
heparin.
In the unsaturated caboxylic acid of formula (II), R.sub.1, R.sub.2
and R.sub.3 are most preferably such that R.sub.1 and R.sub.2 are
hydrogen atoms, and R.sub.3 is a hydrogen atom or a methyl group
(i.e., acrylic or methacrylic acid). The halogen which constitutes
the halide of the unsaturated carboxylic acid is preferably a
chlorine or bromine atom, and the chlorine atom is especially
preferred.
Examples of preferred halides or anhydrides of the unsaturated
carboxylic acid include acryloyl chloride, methacryloyl chloride,
acrylic anhydride and methacrylic anhydride. These compounds have
high activity by themselves, and very readily react with the
alcoholic hydroxyl groups of heparin to form the heparin derivative
of formula (I). The site of an ester linkage in the heparin
derivative may correspond to at least one of the many alcoholic
hydroxyl groups of heparin. No particular limitation is imposed on
the site and number of the ester linkages.
When the acid halide or acid anhydride is liquid in the reaction of
heparin with the acid halide or anhydride of the unsaturated
carboxylic acid, the reaction may be carried out in a homogeneous
solution system or heterogeneous solution system after the addition
of heparin. Preferably, the reaction is carried out in a
homogeneous solution system using a solvent. The solvent that may
be used is substantially non-reactive with the halide or anhydride
of the unsaturated carboxylic acid of formula (II), and may, for
example, be formamide, acetonitrile, chloroform, toluene, etc.
Usually, these solvents have a weak power of dissolving heparin,
and therefore, it is preferred to use heparin after subjecting it
to a solubilizing treatment. Solubilization can be performed, for
example, by convering heparin into its quaternary ammonium salt. A
reagent for conversion to a quaternary ammonium salt may include,
for example, cetyl pyridium chloride, cetyl trimethyl ammonium
bromide, etc. Cetyl pyridium chloride is preferred.
The reaction of heparin (or a quaternary ammonium salt of heparin)
with the acid halide or acid anhydride of the unsaturated
carboxylic acid is conveniently carried out at not more than
100.degree. C., preferably 0.degree. to 70.degree. C., more
preferably at room temperature. Temperatures much higher than
100.degree. C. are undesirable because they result in deactivation
of heparin. The reaction time which depends upon the reaction
temperature is usually about 5 seconds to about 50 hours.
In the esterification reaction using the acid halide and/or acid
anhydride, known esterification catalysts may be used. For example,
basic catalysts such as triethylamine or pyridine may be used.
Other esterification catalysts may also be used. The reaction
product is separated by re-precipitation, etc. and is sufficiently
washed by repeating re-precipitation and washing. As a solvent for
re-precipitation, acetone, chloroform, etc. are used preferably
with a compound capable of removing the acid halide or anhydride of
the unsaturated carboxylic acid by hydrolysis, such as water and
ethanol.
In this manner, the heparin derivative of formula (I) having ester
groups can be easily obtained.
The novel heparin derivative of this invention is useful for
imparing antithrombotic activity to various biomedical materials
having a surface to be in direct contact with the blood.
Examples of the biomedical material which is to be made
antithrombotic by the novel heparin derivative of this invention
include shaped articles such as catheters, blood bags, blood
circuits, A-V shunts for artificial kidneys, dialysis membranes for
artificial kidneys and tubes and pumping chambers for blood pumps.
It is also possible to impart antithrombotic activity to precursors
of these shaped articles, for example films or hollow articles.
The biomedical materials as shaped articles are composed of
thermoplastic resins such as polyethylene, polypropylene, polyvinyl
chloride, polyesters, polyamides, polycarbonates, polyurethanes,
silicone resins and fluorocarbon resins; elastomers such as natural
rubbers, synthetic rubbers, polyester ether elastomers and
polyester ester elastomers; cellulose derivatives such as acetyl
cellulose; and other resins.
Antithrombotic activity can be imparted to the biomedical material
in the form of a shaped article by treating it with actinic light
in the presence of the heparin derivative of this invention. The
phrase "in the presence", as used herein, denotes the condition in
which the surface of the shaped article is in contact with the
heparin derivative, or the heparin derivative is impregnated in the
surface layer portion of the shaped article. Preferably, this can
be achieved by the following procedure. Specifically, the heparin
derivative having an unsaturated group is dissolved to a
concentration of about 0.001 to 100% by weight in a solvent capable
of uniformly dissolving the heparin derivative, such as formamide,
physiological saline or a mixture of water and ethanol, and the
resulting uniform solution is kept in uniform contact with the
blood-contacting surface of the shaped article. In this state, the
surface of the shaped article is treated with actinic light. To
keep the shaped article in uniform contact with the solution, a
dipping method is preferably used by which the shaped article is
dipped in the solution. In this actinic light treatment, the
solvent may be used in combination with an organic solvent miscible
uniformly with it, such as dimethyl formamide, dimethyl sulfoxide,
acetonitrile, alcohols, and dioxane to increase the affinity of the
solution with the shaped article. The concentration of the heparin
derivative in the heparin solution is preferably 0.01 to 50% by
weight, more preferably 0.05 to 10% by weight.
In the above actinic light treatment, an unsaturated monomer to be
exemplfied hereinbelow may be added to the heparin solution in an
amount of 1 to 10,000% by weight. The amount of the unsaturated
monomer is preferably 10 to 5000% by weight, more preferably 50 to
1000% by weight, based on the weight of the heparin derivative.
When the unsaturated monomer is to be used jointly, it is
preferably added to a solution of the heparin derivative. The
unsaturated monomer is preferably an ordinary vinyl compound, and
specific examples include acrylic acid, methacrylic acid, methyl
methacrylate, acrylonitrile, hydroxyethyl methacrylate, styrene,
vinyl chloride, vinylpyridine, and N-vinylpyrrolidone. At least one
of these unsaturated monomers may be used. Preferably, at least one
of them is a hydrophilic unsaturated monomer. Preferred hydrophilic
unsaturated monomers are, for example, acrylic acid, methacrylic
acid, hydroxyethyl methacrylate and N-vinylpyrrolidone. The
hydrophilic unsaturated monomer may be used in an amount 0.1 to 10
times the weight of the hydrophobic unsaturated monomer.
In accordance with this invention, a shaped article having a
surface to be in contact with the blood is exposed to irradiation
of actinic light in the presence of the heparin derivative having
an unsaturated group by, for example, the following procedure (a)
or (b).
(a) Ultraviolet light is irradiated at a temperature of -10.degree.
C. to 70.degree. C., preferably at room temperature, preferably in
the presence of a photoreaction initiator.
(b) Electron beams and gamma-rays are irradiated under the
following conditions.
The dose of irradiation is 0.001 Mrads to 100 Mrads, preferably
0.01 Mrad to 20 Mrads, more preferably 0.02 Mrad to 10 Mrads.
Although the dose does not particularly affect the results, it is
desirable that irradiation be performed uniformly on a shaped
article to be treated. The irradiation temperature may be from
-10.degree. C. to 70.degree. C., and generally, it is
advantageously room temperature.
The procedure (b) is especially preferred.
Many of the thermoplastic resin now used in biomedical materials
are hydrophobic resins such as fluorocarbon resins. To bind the
heparin derivative to a biomedical material composed of a
hydrophobic polymer, it is preferred to hydrophilize the surface of
the hydrophobic polymer prior to the treatment. Hydrophilization
may be performed by any known method, such as grafting of a
hydrophilic unsaturated monomer. For example, it can be
conveniently performed by grafting a hydrophilic unsaturated
monomer such as acrylic acid, methacrylic acid, hydroxyethyl
methacrylate and vinylpyrrolidone by gamma-rays.
The biomedical materials to which antithrombotic activity has been
imparted by the heparin derivative of this invention has much
higher antithrombotic activity than conventional biomedical
materials made from silicon rubbers, and has a reduced danger of
bleeding owing to a large amount of heparin.
It has been found in accordance with this invention that the
surface of a biomedical material can be rendered antithrombotic by
performing the esterification reaction of this invention on the
aforesaid surface. Specifically, antithrombotic activity can be
conveniently imparted to the biomedical material by forming at
least that surface of the material which comes into contact with
the blood from a polymer having a carboxylic acid halide group
and/or a carboxylic anhydride group in the side chain, and treating
the resulting material with a heparin solution.
The polymer from which the blood-contacting surface of the
biomedical material is made has a carboxylic halide group (--COX in
which X is halogen) and/or a carboxylic anhydride group (--COOCO--)
in the side chain of the molecule. Introduction of such groups into
the side chain of a polymer can, for example, be performed by
addition-polymerizing a halide or anhydride of a carboxylic acid
having at least one carbon-carbon double bond in the molecule, or
reacting it with another polymer. Examples of such a compound are
the monohalides, dihalides and anhydrides of unsaturated carboxylic
acids such as acrylic acid, methacrylic acid, maleic acid and
cyclohexene-dicarboxylic acid. These compounds may be used either
singly or as a mixture of two or more.
Examples of the polymer having a carboxylic acid halide group
and/or a carboxylic anhydride group in the side chain include a
polymer or copolymer obtained by addition-polymerization of the
aforesaid compound; a copolymer obtained by addition-polymerization
of the aforesaid compound with another monomer having a
carbon-carbon double bond such as ethylene, propylene, vinyl
chloride, styrene, acrylonitrile or butadiene; a graft copolymer
obtained by graft copolymerizing the polymer of the aforesaid
compound with the aforesaid monomer; a graft copolymer obtained by
graft polymerizing a polymer of the aforesaid monomer with the
aforesaid compound; a copolymer graft copolymer obtained by graft
polymerization of the aforesaid compound with a known thermoplastic
polymer or a flexible polymer such as a polyester, polyamide,
polycarbonate, polyurethane, silicone resin, natural rubber or
synthetic rubber; and mixtures of two or more of these.
Examples of the polyesters which form graft copolymers or matrix
polymers by reaction with the carboxylic acid halide or carboxylic
anhydride are polyethylene terephthalate, polytetraethylene
terephthalate, polyethylene-2,6-naphthalate, polyhexamethylene
terephthalate, and copolyesters of these polyesters with a minor
proportion of at least one compound having an ester-forming group,
such as adipic acid, dodecanedionic acid, trimellitic acid,
isophthalic acid, phthalic acid, neopentyl glycol, hexamethylene
glycol, pentaerythritol, polyethylene glycol or polytetramethylene
glycol. Examples of the polyamide are polycaprolactam and
polyhexamethylene adipate. Examples of the polycarbonate are
aromatic polycarbonates derived from bisphenols such as bisphenol
A, bisphenol Z and bisphenol S and phosgene or diphenyl carbonate.
A dimethylsiloxane polymer is an example of the silicone resin.
These polymers may be prepared by conventional known methods. In
the present invention, all of the carboxylic acid halide groups or
carboxylic anhydride groups in the side chain of the polymers
should not be converted to carboxyl groups or other groups by
hydrolysis before contact with the heparin solution. In the
production of the polymers, therefore, it is preferred not to use a
polymer or a reaction aid which has the function of converting the
carboxylic acid halide group or the carboxylic anhydride group to a
carboxyl group. Those polymers or reaction aids which convert only
some of the carboxylic acid halide groups or carboxylic anhydride
groups into carboxyl groups and do not substantially impair the
objects of this invention may be used depending upon the ratio of
conversion. For example, in the production of a polymer by
suspension-polymerization or solution-polymerization, it is
preferred to use a compound inert to the carboxylic acid halide
group and/or the carboxylic anhydride group as a solvent.
Furthermore, when a polymer swelling agent is used in the
production of a graft copolymer or a matrix polymer, the swelling
agent is preferably inert to the carboxylic acid halide group and
the carboxylic anhydride groups.
The swelling agent may be selected from known organic solvents, and
may be those which after a certain period of time from contact with
the polymer at room temperature or at a suitable temperature,
penetrate into the inside of the polymer at the contacting surface
and cause changes in its volume, weight, shape, etc.
Specific examples of such solvents are acetonitrile, methylene
chloride, tetrahydrofuran and dimethylnaphthalene for copolyesters;
monochlorobenzene, methylene chloride and decalin for polyolefins;
and methylene chloride and dioxane for polycarbonates.
These are only part of the examples, and suitable swelling agents
may be selected depending upon the desired degree of swelling and
the type and quality of the polymer.
The graft copolymer or matrix polymer having a carboxylic acid
halide group and/or a carboxylic anhydride group in the side chain
can be easily obtained by dipping a base polymer in a solution
containing the desired proportions of a carboxylic acid halide or a
carboxylic anhydride and the swelling agent for the polymer to
swell the polymer and heating the polymer in the dipped state or
after withdrawing from the solution, or irradiating actinic light
on such a polymer. The solvent used at this time is preferably
selected from those exemplified above as the swelling agent.
Examples are monochlorobenzene for dissolving polyethylene under
heat, and chloroform for dissolving polytetramethylene glycol
copolybutylene terephthalate. The actinic light used at this time
includes light energy in the broad sense such as ultraviolet light
or microwaves, and ionizing radiations such as electron beams,
gamma-rays, X-rays, and neutron rays. The ultraviolet light,
electron beams and gamma-rays are especially preferred. At this
time, it is preferred to include a polymerization promotor in the
dipping solution. In the case of the heat reaction, a radical
initiator such as benzyl peroxide and dicumyl peroxide is preferred
as the polymerization promotor. In the case of ultraviolet
irradiation, a sensitizer such as benzophenone and benzil ketal is
preferred.
The shaped article whose surface in contact with the blood is
formed of the polymer having a carboxylic acid halide group and/or
a carboxylic anhydride group in the side chain can be easily
obtained by shaping the aforesaid polymer in a manner in a
conventional manner. Or it can be obtained by laminating the
polymer to the surface of a shaped article by a melting method or a
casting method. Or it can be obtained by shaping the base polymer
in a conventional manner to form a shaped article, then reacting
the surface of the resulting shaped article with a carboxylic acid
halide or a carboxylic anhydride to change the surface to that of a
graft copolymer or a matrix polymer. The last method is most
preferred.
The shaped article to the surface of which is laminated a polymer
having a carboxylic acid halide group and/or a carboxylic anhydride
group in the side chain is produced from a thermoplastic resin such
as polyethylene, polypropylene, polyesters, polyamides,
polycarbonates, polyurethane or silicone resins, an elastomer such
as natural rubber, synthetic rubbers, polyester ether elastomer, or
polyester ester elastomer, and other resin.
Desirably, the polymer having carboxylic acid halide groups and/or
carboxylic anhydride groups in the side chain has at least
10.sup.-9 equivalent/cm.sup.2, preferably at least 10.sup.-8
equivalent/cm.sup.2, especially preferably at least 10.sup.-7
equivalent/cm.sup.2, of the aforesaid carboxylic acid halide groups
and/or the carboxylic anhydride groups at that part or surface of
the shaped article to which antithrombotic activity is to be
imparted. The amount of these groups can be determined by known
methods such as titration or back titration using a neutralization
reaction, X-ray determination of the amount of metal by metal salt
exchange, etc.
The resulting shaped article is then contacted with the heparin
solution. At this time, all of the carboxylic acid halide groups or
carboxylic anhydride groups should not be changed to carboxyl
groups by hydrolysis, etc.
The heparin solution used in this invention is a solution of
heparin in an organic solvent. The organic solvent may be an
ordinary organic solvent which does not have the property of
changing all of the carboxylic acid halide groups or carboxylic
anhydride groups into carboxyl groups by hydrolysis, etc. Examples
are methylene chloride, formamide, and a mixture of dimethyl
sulfoxide and chloroform.
Commercially available heparin (sodium salt) is dissolved in the
organic solvent to prepare the heparin solution. When heparin is
insoluble or sparingly soluble, it is necessary to subject it to a
solubilizing treatment. Solubilization can easily be achieved by
converting heparin into its quaternary ammonium salt. A reagent for
conversion to the quaternary ammonium salt may, for example, be
cetyl pyridium chloride and cetyl trimethyl ammonium bromide. Cetyl
pyridium chloride is preferred. The concentration of heparin, for
example solubilized heparin, is not more than about 10% by weight,
preferably 1 to 5% by weight.
Treatment with the heparin solution is carried out by contacting
the shaped article with the solution. The contacting time is at
least 10 seconds, preferably 30 seconds to 30 hours, especially
preferably 1 minute to 5 hours. The temperature at which the
contacting is carried out is not more than 100.degree. C.,
preferably not more than 50.degree. C., especially preferably at
room temperature. Desirably, the treating time and temperature are
selected depending upon the relation of the swellability of the
polymer forming the surface to be treated to the solvent in the
heparin solution. At the time of the treatment, a known
esterification catalyst may be used such as a basic catalyst (e.g.,
triethylamine or pyridine).
The biomedical material can be rendered antithrombotic by the
heparin derivative of this invention by binding heparin to that
surface of the shaped article of the polymer having the specified
groups which makes direct contact with the blood. The resulting
antithrombotic biomedical material has much higher antithrombotic
activity than those made from silicone rubbers which have been
previously used for medical treatment, and has a reduced danger of
bleeding owing to a large amount of heparin.
The following Examples illustrate the present invention in greater
details. In these examples, all parts and percentages are by weight
unless otherwise indicated.
Heparin used in the Examples was a product of Eastman Kodak Co.
Other reagents were either those specified in Japanese
Pharmacopoeia, or class 1 reagents.
The rabbit blood used in the antithrombosis test was prepared by
mixing the blood taken from the vein of the rabbit ear with a 3.8%
aqueous solution of sodium citrate in a volume ratio of 9:1,
maintaining the resulting mixture at 37.degree. C. for 1 minute,
and then mixing it with the same volume of a 1/40 M aqueous
solution of calcium chloride.
EXAMPLE 1
Heparin (5 parts) and 1.5 parts of acrylic anhydride were dissolved
in 100 parts of formamide, and reacted at room temperature for 48
hours with stirring. Acetone (1000 parts) was added to the reaction
mixture to form a precipitate. The precipitate was separated by
filtration, and re-dissolved in 40 parts of water. Then, the
solution was subjected to re-precipitation using 1000 parts of
ethanol. The precipitate was subjected to two cycles of
re-precipitation and washing with water-ethanol, and the product
was dried in vacuo at 25.degree. C. to obtain 4 parts of a white
solid.
The infrared adsorption spectrum of the white solid is shown in
FIG. 1. This spectrum was substantially the same as that of the
starting heparin except that a new absorption of the ester linkage
was seen at 1720 cm.sup.-1.
The white solid turned brown at 240.degree. to 250.degree. C. as
does the starting heparin. The elemental analysis values for the
white solid were 21.23% C., 3.74% H and 1.85% N, while those of the
starting heparin were 20.42% C, 3.58% H and 1.88% N. The infrared
absorption spectrum of the starting heparin is shown in FIG. 4.
By the following calculation from the above elemental analysis
values, it was found that about 8.5%, based on the hydroxyl groups
of heparin, of acrylic acid was introduced through an ester
linkage.
Heparin is a polymeric compound having a disaccharide of the
following structural formula ##STR6## as one unit. (Not all of the
units have three SO.sub.3 H as in the above formula, but this is
irrelevant to the calculation of the ratio of introduction of
acrylic acid.)
Since the number of carbon atoms in one unit is 12, the molecular
weight (H) of one unit of heparin is calculated as follows from the
amount (20.42%) of carbon determined by elemental analysis.
##EQU2##
When methacrylic acid is introduced through an ester linkage, the
structural formula of the unit changes to the following.
##STR7##
As a result of esterification, 4 carbon atoms increased for each
unit, and the increase of the molecular weight was 68.08.
Hence, the ratio of introduction (D%) of methacrylic acid per two
hydroxyl groups (i.e. per unit) is calculated as follows from the
amount (21.23%) of carbon determined by elemental analysis of the
heparin ester. ##EQU3##
Hence, the ratio of introduction per hydroxyl group is
17.0/2=8.5(%).
The resulting white solid was added in each of the amounts shown in
Table 1 to the rabbit blood, and gently held at 37.degree. C. in a
glass test tube. The time which elapsed until a thrombus formed was
measured. The results are shown in Table 1.
For comparison, the thrombus formation test was conducted using
heparin instead of the heparin derivative. The results are also
shown in Table 1.
TABLE 1 ______________________________________ Time elapsed until
the Amount added formation of a thrombus Antithrombotic agent
(mg/ml) (minutes) ______________________________________ Heparin
derivative 0.001 7 obtained in Example 1 0.01 21 0.001 9 Untreated
heparin 0.01 19 ______________________________________
It is seen from the results obtained that the antithrombotic
activity of the heparin derivative having acrylic acid introduced
thereinto was equivalent to that of heparin.
EXAMPLE 2
Ten parts of cetyl pyridium salt of heparin was dissolved in a
mixture of 70 parts of dimethyl sulfoxide and 30 parts of
chloroform, and 10 parts of methacrylic anhydride was added. The
mixture was reacted at 40.degree. C. for 3 hours. The reaction
product was re-precipitated once with chloroform-ethyl ether and
twice with water-ethanol, and then treated with a 2.1 M aqueous
solution of sodium chloride. Sodium chloride was removed by using a
cellophane membrane in a customary manner, and the residue was
reprecipitated with water-ethanol and washed to separate 3 parts of
a white solid as a purified product.
In the same way as in Example 1, 0.01 mg/ml of the white solid was
added to the rabbit blood, and its antithrombotic activity was
observed. The time which elapsed until a thrombus was seen to form
was 20 minutes. The infrared absorption spectrum of the white solid
is shown in FIG. 2. The spectrum showed an absorption of the ester
group at 1720 cm.sup.-1 which was not present in the heparin before
the reaction. Furthermore, the white solid turned brown at
240.degree. to 250.degree. C. The elemental analysis values of the
white solid were 22.01% C, 3.62% H and 1.91% N, and the amount of
methacrylic acid introduced was 13% based on the hydroxyl
groups.
EXAMPLE 3
Heparin (1.5 parts) and 0.5 part of methacryloyl chloride were
added to 25 parts of formamide, and 0.5 part of pyridine was added.
The mixture was reacted at room temperature for 0.5 hour.
The reaction product was re-precipitated with water-cooled ethanol,
and again dissolved in water. It was again precipitated with a
mixture of ethanol and chloroform (60:40 by volume) to separate a
white solid as a purified product.
The infrared absorption spectrum of the resulting white solid is
shown in FIG. 3. The spectrum showed an absorption of the ester
linkage at 1720 cm.sup.-1. The white solid turned brown at
240.degree. to 250.degree. C. The elemental analysis values of the
white solid were 23.07% C, 3.64% H and 1.92% N, and 21% of the
hydroxyl groups of heparin were esterified with methacrylic
acid.
EXAMPLE 4
Example 3 was repeated except that the amount of the methacryloyl
chloride was changed to 0.05 part, and the amount of pyridine was
changed to 0.05 part.
The resulting white solid was found to be methacrylic
acid-introduced heparin having a ratio of introduction of ester
groups of 1.2% calculated from the amount of carbon (20.53%)
determined by elemental analysis. In the infrared absorption
spectrum of the white solid, a shoulder ascribable to the ester was
noted at 1720 cm.sup.-1.
EXAMPLE 5
Example 3 was repeated except that the amount of the methacryloyl
chloride was changed to 1.5 parts, and the amount of the pyridine
was changed to 1.5 parts, and the reaction temperature was changed
to 50.degree. C.
The resulting white solid was found to be methacrylic
acid-introduced heparin having a ratio of introduction of ester
groups of 54% calculated from the amount of carbon (25.15%)
determined by elemental analysis. In the infrared absorption
spectrum of the white solid, a sharp absorption ascribable to the
ester groups was seen at 1720 cm.sup.-1.
EXAMPLE 6
Polytetramethylene terephthalate (reduced specific viscosity 2.31
dl/g) having copolymerized therewith 60% of polytetramethylene
glycol having a molecular wtight of 2000 was made into chips. The
chips were passed through an extruder at 250.degree. C., and
extruded from a slit having a width of 0.5 mm fitted to its tip to
make a sheet having a thickness of 0.5 mm.
One piece of the sheet was cut out, put into a petri dish and was
impregnated entirely with a solution prepared by mixing 100 parts
of acetonitrile with 1 part of acrylic acid and 1 part of cetyl
pyridium salt of heparin derivative obtained by treating the
heparin derivative with an aqueous solution of cetyl pyridium
chloride.
Gamma-rays were irradiated in a dose of 0.1 Mrad onto the petri
dish containing the sheet sample. Then, the sheet was taken out,
washed with acetonitrile, fully washed successively with a 50%
aqueous solution of methylene chloride and ethanol, a 2.1 M aqueous
solution of sodium chloride, and pure water, and dried.
The resulting sheet was dipped in an aqueous solution of toluidine
blue to test the color formation of heparin. The sheet formed a
reddish violet color, and thus, the presence of heparin was
ascertained.
EXAMPLE 7
Ten parts of cetyl pyridium salt of heparing was dissolved in a
mixture of 70 parts of dimethyl sulfoxide and 30 parts of
chloroform, and 10 parts of acrylic anhydride was added. The
mixture was reacted at 40.degree. C. for 3 hours. The resulting
product was re-precipitated once with chloroform-ethyl ether and
twice with water-ethanol and then treated with a 2.1 N aqueous
solution of sodium chloride. Then, in a customary manner, sodium
chloride was removed by using a cellophane membrane. The residue
was further re-precipitated with water-ethanol and washed. The
resulting solid white solid turned brown at 240.degree. to
250.degree. C., and from the elemental analysis values, the amount
of acrylic acid introduced was found to be 13% based on the
hydroxyl groups of heparin.
The cetyl pyridium salt of heparin used was obtained by reacting
heparin (a product of Eastman Kodak Co., conforming to the
standards of U.S. Pharmacopoeia) with cetyl pyridium chloride in a
customary manner.
Ten parts of a polyester ester block copolymer (having a reduced
specific viscosity of 1.53 dl/g measured at 35.degree. C. in
ortho-chlorophenol in a concentration of 1.2 g/dl) obtained by
copolymerizing 67% of polycaprolactone, 10% of polyethylene
terephthalate and 23% of polybutylene terephthalate was dissolved
in 100 parts of chloroform. The solution was coated on a glass test
tube having an inside diameter of about 1 cm and a length of about
10 cm, and dried. Then, the test tube was filled with a solution
prepared by dissolving 1 part of the heparin esterified with
acrylic acid in 100 parts of water-ethanol (50:50 by weight), and
gamma-rays were irradiated in a dose of 0.1 Mrad onto the test
tube. The test tube was fully washed with water-ethanol (50
parts-50 parts), physiological saline and water, and air-dried at
room temperature.
An aqueous solution of toluidine blue was put into the test tube. A
color of reddish violet formed, and the presence of heparin was
ascertained.
The blood taken from a rabbit was put into the test tube not
subjected to the color formation test, and hemolysis and thrombosis
were examined. The results are shown in Table 2.
TABLE 2 ______________________________________ Time of contact with
the blood Test items 20 min. 1 hour 3 hours
______________________________________ Example 7 Hemolysis No No No
Thrombosis No No No Comparative Hemolysis No -- -- Example 1
Thrombosis Yes -- -- ______________________________________
In Table 2, Comparative Example 1 refers to the case of coating a
siliconize surface treating agent (a product of Fuji Systems Co.,
Ltd.) on the glass test tube.
EXAMPLES 8 TO 10 AND COMPARATIVE EXAMPLES 2 TO 4
Heparin (15 parts) and 0.5 part of methacryloyl chloride were added
to 25 parts of formaldehyde, and 0.5 part of pyridine was further
added. The mixture was reacted at room temperature for 0.5 hour.
Then, the reaction product was re-precipitated with ice-cooled
ethanol, and again dissolved in water. The mixture of ethanol and
chloroform (volume ratio 60:40) to separate a white solid as a pure
product. The white solid turned brown at 240.degree. to 250.degree.
C. Elemental analysis led to the determination that the white solid
resulted from esterification of 21% of the hydroxyl groups of
heparin with methacrylic acid.
Five parts of a polyester polyether block copolymer having a
reduced specific viscosity (measured at 35.degree. C. in
ortho-chlorophenol in a concentration of 1.2 g/dl) of 2.31 g/dl and
having copolymerized therewith 60% of polytetramethylene glycol
having a molecular weight of 2000 was dissolved in 100 parts of
chloroform. The solution was coated on a glass test tube having an
inside diameter of about 1 cm and a length of about 10 cm, and
dried. The test tube was then filled with a solution obtained by
dissolving 0.67 part of methacrylic acid-introduced heparin in 100
parts of a mixture of physiological saline and ethanol in a volume
ratio of 70:30, and adding acrylic acid to the solution in the
amounts indicated in Table 3. Gamma-rays were irradiated on the
test tube at a dose of 0.1 Mrad. The test tube was thoroughly
washed with physiological saline and then with water, and dried in
the air at room temperature.
When an aqueous solution of toluidine blue was put into the test
tube, a color of reddish violet formed. Hence, the presence of
heparin was ascertained.
The same blood test as in Example 7 was performed, amnd the results
are shown in Table 3.
TABLE 3 ______________________________________ Example (Ex.) or
Amount Compara- of Time of contact tive acrylic with the blood
Example acid 20 1 2 3 (CEx.) (parts) Test items min. hour hours
hours ______________________________________ Ex. 8 0 Hemolysis No
Yes -- -- Thrombosis No Yes -- -- Ex. 9 0.67 Hemolysis No No No --
Thrombosis No No Yes -- Ex. 10 3.30 Hemolysis No No No No
Thrombosis No No No Yes CEx. 2 0 Hemolysis No -- -- -- Thrombosis
Yes -- -- -- CEx. 3 0 Hemolysis No No -- -- Thrombosis No Yes -- --
CEx. 4 0 Hemolysis No No -- -- Thrombosis No Yes -- --
______________________________________
Comparative Example 2 refers to the case of coating the glass tube
with a siliconize surface treating agent (a product of Fuji Systems
Co., Ltd.). In Comparative Example 3, 0.01 mg/ml of heparin was
added to the rabbit blood. in Comparative Example 4, the aforesaid
methacrylic acid-introduced heparin was added.
EXAMPLES 11 TO 13 AND COMPARATIVE EXAMPLES 5 TO 7
Heparin (1.5 parts), 0.1 part of methacryloyl chloride and 0.1 part
of pyridine were added to 25 parts of formamide, and reacted at
room temperature for 0.5 hour. The reaction mixture was worked up
in the same way as in Example 8 to obtain heparin having 7% of
methacrylic acid introduced thereinto based on the hydroxyl groups
of heparin.
Acetyl cellulose (10 parts) was dissolved in 100 parts of acetone,
and the solution was coated on a glass test tube having an inside
diameter of 1 cm and a length of about 10 cm and dried. Acrylic
acid was added in the amounts indicated in Table 4 to a solution of
0.67 part of the resulting heparin derivative in 100 parts of
physiological saline. The resulting solution was filled into the
coated test tube. Gamma-rays were irradiated onto the test tube at
a dose of 0.1 Mrad. The test tube was washed with physiological
saline and then with water, and air-dried at room temperature. The
presence of heparin in the test tube was determined by color
formation using an aqueous solution of toluidine blue.
Using the resulting test tube, the same blood test as in Example 7
was performed, and the results are shown in Table 4.
TABLE 4 ______________________________________ Example (Ex.) or
Compara- Amount of tive acrylic Time of contact Example acid with
the blood (CEx.) (parts) Test items 20 min. 1 hour 2 hours
______________________________________ Ex. 11 0 Hemolysis No -- --
Thrombosis Yes -- -- Ex. 12 0.67 Hemolysis No No No Thrombosis No
No Yes Ex. 13 3.30 Hemolysis No No No Thrombosis No No No CEx. 5 0
Hemolysis No -- -- Thrombosis Yes -- -- CEx. 6 0 Hemolysis No No --
Thrombosis No Yes -- CEx. 7 0 Hemolysis No No -- Thrombosis No Yes
-- ______________________________________
In Comparative Example 5, the glass test tube was coated with a
siliconize surface treating agent (a product of Fuji Systems Co.,
Ltd.). In Comparative Example 6, heparin was added to the rabbit
blood at a rate of 0.01 mg/ml. In Comparative Example 7, the
methacrylic acid-introduced heparin was added at a rate of 0.01
mg/ml.
EXAMPLE 14
A cannula made of Teflon (trademark) was dipped in fully deaerated
acrylic acid. The system was sealed up with nitrogen, and
gamma-rays were irradiated at room temperature from Co 60 for 1
hour at a dose of 0.1 Mrad/hr. After the irradiation, the cannula
was fully washed and dried. The ratio of grafting was 2%. The ratio
of grafting was calculated from the following equation.
##EQU4##
The graft-treated cannula was dipped in a solution prepared by
dissolving 2 parts of the same methylacrylic acid-introduced
heparin as in Example 8 in a mixture of water and methanol (70:30
by volume) and adding 5 parts of acrylic acid. The system was
sealed up with nitrogen, and gamma-rays were again irradiated at
room temperature at a dose of 0.1 Mrad. The treated cannula was
fully washed, and dipped in an aqueous solution of toluidine blue.
A color of reddish violet formed, and thus, the presence of heparin
was ascertained.
EXAMPLE 15
A polyester ether block copolymer (reduced specific viscosity 2.90
dl/g; measured at 35.degree. C. in orthochlorophenol in a
concentration of 1.2 g/dl) was prepared from 33 parts of a hard
segment obtained by the reaction of a mixture of ethylene glycol
and tetramethylene glycol (33:67 by mole) with dimethyl
terephthalate and 67 parts of a soft segment derived from
polytetramethylene glycol having a molecular weight of 2000. Chips
of the copolymer were extruded through a tube die under ice cooling
to obtain a transport tube having an inside diameter of 3 mm and an
outside diameter of 5 mm.
The tube was cut to a length of 25 cm and both ends were tapered.
The tapered tube was dipped in a solution prepared by dissolving 2
parts of the same methacrylic acid-introduced heparin in a mixture
of physiological saline and methanol (70:30 by volume) and adding 5
parts of acrylic acid. The system was sealed up with nitrogen, and
gamma-rays were irradiated at room temperature for 1 hour at a dose
of 0.1 Mrad/hr. After the irradiation, the tube was fully washed,
and dried.
The treated tube was connected to the carotid vein of an adult dog
through the carotid artery, and embedded in the skin. It was
subjected to a long-term antithrombosis test. No thrombus formation
was noted for a period of more than 40 days, and the tube showed
excellent antithrombotic activity.
EXAMPLES 16 AND 17 AND COMPARATIVE EXAMPLES 8 AND 9
Five parts of a polyester polyether block copolymer having a
reduced specific viscosity, measured at 35.degree. C. in
ortho-chlorophenol in a concentration of 1.2 g/dl, of 2.31 dl/g and
composed of polytetramethylene terephthalate having copolymerized
therewith 60% of polytetramethylene glycol having a molecular
weight of 2000 was dissolved in 100 parts of chloroform. The
solution was coated on a glass test tube having an inside diameter
of about 1 cm and a length of about 10 cm.
The test tube was then filled with a solution of acrylic anhydride
in the amounts indicated in Table 5 in 100 parts of acetonitrile.
Gamma-rays were irradiated onto the test tube at a dose of 0.1
Mrad. The test tube was fully washed with acetonitrile and then
dried to form a composite polymer-coated test tube.
Separately, heparin purschased from Eastman Kodak Co. (conforming
to the standards of U.S. Pharmacopoeia) was dissolved in a 0.04
mole aqueous solution of NaCl, and cetyl pyridium chloride was
added to precipitate a cetyl pyridium salt of heparin. The heparin
salt was separated by filtration, washed and dried. The product (2
parts) was dissolved in 100 parts of methylene chloride. The
heparin solution obtained was filled into the composite
polymer-coated test tube, and allowed to stand for 1 minute. Then,
the test tube was successively washed with a 50% aqueous solution
of ethanol, a 2.1 M aqueous solution of NaCl and pure water, and
then dried.
When an aqueous solution of toluidine blue was put into the test
tube, a color of reddish violet formed. Hence, the presence of
heparin was ascertained.
The rabbit blood was put into the test tube not subjected to the
color formation test, and observed at 37.degree. C. for hemolysis
and thrombosis. The results are shown in Table 5.
TABLE 5 ______________________________________ Example (Ex.) or
Compara- Amount of tive acrylic Time of contact Example anhydride
with the blood (CEx.) (parts) Test items 10 min. 1 hour 3 hours
______________________________________ Ex. 16 1 Hemolysis No No No
Thrombosis No No No Ex. 17 10 Hemolysis No No No Thrombosis No No
No CEx. 8 0 Hemolysis No Yes -- Thrombosis No Yes -- CEx. 9 0
Hemolysis No -- -- Thrombosis Yes -- --
______________________________________
In Comparative Example 8, the rabbit blood was added to heparin at
a rate of 0.002 mg/ml. In Comparative Example 9, a siliconize
surface treating agent (a product of Fuji Systems Co., Ltd.) was
coated on the test tube.
EXAMPLE 18
A solution of 50 parts of acrylic anhydride in acetonitrile was
subjected to irradiation of gamma-rays at a dose of 0.1 Mrad. The
reaction product was separated by filtration, and dried. The
resulting polymeric compound was a white non-tacky solid.
Five parts of a cetyl pyridium salt of heparin was dissolved in a
mixture consisting of 70 parts of dimethyl sulfoxide and 30 parts
of chloroform, and 5 parts of the polymeric compound was added. The
resulting heterogenous solution was stirred to form a solution of
the heparin derivative.
The solution was coated on a glass test tube in the same way as in
Example 16, washed, and dried. Using the coated test tube, the
rabbit blood was tested. As a result, even after a lapse of 3
hours, the blood showed no hemolysis nor thrombosis.
EXAMPLE 19
Polyethylene terephthalate having copolymerized therewith 70% of
caprolactone was melted and molded into a tube having an inside
diameter of 5 mm and an outside diameter of 8 mm. One end of the
tube was then sealed.
The tube was filled with a solution of 5 parts of acryloyl chloride
in 95 parts of toluene, and gamma-rays were irradiated thereon at a
dose of 0.1 Mrad. Using the resulting tube, the same blood test as
in Example 16 was performed. After standing for 3 hours, the blood
showed no hemolysis nor thrombosis.
* * * * *